Add basic block biquad test

Author: jepler

tests/circuitpython/synthio_block_biquad.py

@@ -0,0 +1,16 @@
+from synthnotehelper import *
+from synthio import BlockBiquad, FilterType
+import random
+
+random.seed(41)
+
+white_noise = array.array('h', [random.randint(-32000, 32000) for i in range(600)])
+
+@synth_test_rms
+def gen(synth):
+    l = LFO(sweep, offset=1440, scale=2880, rate=.025, once=True)
+    yield [l]
+    b = BlockBiquad(FilterType.LOW_PASS, l)
+    n = Note(100, filter=b, waveform=white_noise)
+    synth.press(n)
+    yield 20